We have Newsletter installed (among other plugins) on a client’s site with a VPS server that has huge traffic. The plugin was updated on December 4th to version 4.7.3. Out of a sudden server cpu started to spike on a huge scale on December 9th. Normally cpu load is about 1.5 to 3.0, and now it was going berserk at 200 to 350! We started disabling plugins until we disabled Newsletter plugin and everything seemed to go down to normal.
We then went to the database to see if there was a crashed table or something in mysql causing the spike, but everything seemed normal. Only newsletter_stats table had an overhead of 64kb, which we optimized.
The people that own the website sent a newsletter every two to three days to about 7000 double opt-in users and we’re sure they’re going to growl because now they can’t sent it. Is there anything you can help us with so we can find out the cause of this cpu spike, that seems to be caused by the plugin?
Also, this has happened to two different servers. Even though I updated the plugin to 4.7.4 and WordPress to version 4.7.
I also found that this happens when Newsletter is enabled along with Jetpack plugin. When I disable Newsletter, it still uses more amount of ram and cpu than usual, but considerably lower than before. And when I also disable Jetpack it goes down to normal usage after a while. Now, when I only enable Jetpack again, cpu and ram usage is normal. After that, when I enable Newsletter and starts the delivery, in a few minutes the whole server starts to slow down to a halt.
Maybe it’s something funky with these two plugins enabled, I don’t know. What I know is that we need Jetpack, as we need Newsletter, but can’t use it now.